What is molecular biology?
Molecular biology has revolutionised modern science. But what is it? And what are molecular biologists trying to achieve?
Sickle cell disease is a crippling inherited blood disorder. Sufferers endure awful circulatory problems, anaemia, a high risk of stroke, susceptibility to infection, and a host of other nasty complications. Like many diseases, we can look at it from many different angles. Physiologists study the problems of blood flow. Cell biologists focus on how the affected blood cells look and behave. Biochemists examine the function of blood’s protein building blocks. Geneticists chart the inheritance patterns of the condition.
These different approaches all contribute useful insights. But it is not obvious how each type of explanation impacts the next. Molecular biology, at least as it was first conceived in the middle of the last century, is different.
Like the biochemists, molecular biologists spend most of their time thinking about the molecular cogs, rivets and fly-wheels of living cells. Unlike classical biochemists1, they strive to put all the different perspectives into a bigger picture. They want to make sense of the phenomena of life at a macro-scale by working out the molecular nitty-gritty at the micro-scale. Ideally they want to trace an unbroken chain of causation all the way from the molecular level to the population level.
This needs a bit of explanation. Sickle cell disease illustrates the approach well. During the 1940s and 50s Linus Pauling, one of the founding fathers of molecular biology, changed the way we think about disease forever. Pauling set out to understand the root cause of sickle cell disease in terms of molecular changes within our cells.
We now know that a single-letter change in the DNA code of a single gene causes a minute alteration in the production of haemoglobin, blood’s key oxygen-carrying molecule. The defective haemoglobin is sticky and prone to form aggregates. The aggregates in turn cause red blood cells to become stiff, sickle-shaped (hence the name of the disease) and prone to choke up the body’s smallest blood vessels. These blockages cause many of the symptoms of sickle cell disease.
Such a holistic description of a disease is extremely useful. The key molecular change to DNA helps makes sense of the patient’s whole-body symptoms. This makes diagnosis easy and ensures treatments are effective. But the molecular description also exposes some of the basic principles governing cellular life. It reveals the logic of how our DNA contains the instructions to produce the protein building blocks of cells, which in turn build our tissues and organs.
Molecular biology came into being as a truly inter-disciplinary endeavour. The first molecular biologists borrowed equipment, philosophy and data from the other branches of biology and from physicists, chemists, mathematicians and information theorists. By drawing all these strands together they built a completely new science.
Biology is no longer the dry domain of collectors, hoarders and describers. In the molecular age biologists can make clear predictions, test them and translate the results into action.
We now have a pretty good grasp of how cellular life works in terms of chemical reactions between molecules. There are still a lot of details to iron out, but the real fun will come when we start putting this new knowledge to work. Knowing how something works gives you the power to change it. We’ve now got the tools to rationally re-engineer cells, human and non-human alike, to do our bidding. Deciding when and how to wield these tools is going to elicit some interesting ethical debate.
Originally published at moleculartinkering.wordpress.com on September 18, 2014.
